relay BMW 528I TOURING 1999 E39 Level Control System Manual

18
Level Control Systems
Air Supply System (LVA)
The air supply system is identified as the LVA in the diagnosis program and in the repair
manual. It is mounted in the spare tire well compartment. The components are housed in
a sound deadening carrier, through rubber bushings, to prevent operating noises from
being transmitted through the vehicle’s interior.
With the exception of the compressor relay, individual replacement parts for the air supply
system are not available. If diagnosis determines a defect in any of the other air system
components, complete replacement is necessary.
The air supply system consists of the following components:
 Compressor assembly with;
- Piston compressor
- Electric motor
- Air dryer (desiccator)
- Pressure relief solenoid valve
- Pressure maintenance valve
- Check valves
 Compressor Relay (Replaceable)
 Solenoid Valve Block (2 - two way
valves)
 Lines - including distributor
E39 Features 05

19
Level Control Systems
Air Supply System (LVA) Operation
The single stage piston compressor produces a maximum pressure of 13.5 Bar. The com-
pressor is maintenance free - provided it is used in a dust free environment. This includes
the compressor’s intake air filter.
The compressor is driven by a DC motor that is controlled by the compressor relay through
the control module.
When the compressor is activated, the pressure builds up to a working pressure of 11.4
Bar (+0.8/-1.5 Bar). This is controlled through the pressure maintenance valve. The air
under pressure is fed through the dryer and check valve to the solenoid valve block for the
air springs.
There is one solenoid valve in the valve block for each air strut. This allows the system to
compensate for uneven loads in the vehicle and maintain the vehicles ride height at all
times.
Pressure is drained through the left or right solenoid valve (energized open) the pressure
relief solenoid valve, restrictor, check valve and dryer back to the inlet side of the compres-
sor pump.
LVA Location X5

33
Level Control Systems
Air Suspension Strut
Rear
Minor modifications were made to the rear axle air springs. The air springs and the dampers
are configured separately at the rear axle.
Front
The air suspension replaces the steel suspension at the front axle, i.e. the spring bellows is
attached to the damper. The front air suspension strut and the impact absorber form a
complete unit.
Control Unit
The EHC2 Control Unit is located behind the glovebox adjacent to the General Module.
The connector is a black 54 pin connector.
Inputs received directly into the control unit are:
Ride Height Level Sensor (X4) Up and Down requests from the switch assy.
General Module (Load cutout signal) CAN Bus Inputs
K Bus Inputs Pressure Sensor
Compressor Temperature
O Ou
ut
tp
pu
ut
ts
s
i
in
nc
cl
lu
ud
de
e:
:
Air Unit Control (Activation) Front and Rear Axle Valves
LED’s for Switch Unit Compressor Relay
Pressure Accumulator
Air Suspension Strut
1. Auxiliary Spring
2. Air Bellows
3. Damper

43
Level Control Systems
Components (E65/E66)
Air Supply Unit (LVA)
The air supply unit is located in the spare tire recess and consists of the following compo-
nents:
 Protective cover with internal acoustic
insulation
 Lid
 Rubber-mounted component carrier
 Compressor Unit
 Compressor Relay
 Solenoid Valve Block
IndexExplanationIndexExplanation
1Rubber Mount6Air Drier
2Component Carrier7Compressor
3Compressor Relay8Solenoid Valve, Right
4Electric Motor9Solenoid Valve, Left
5Air Cleaner